Congenital esotropia affects approximately 1% of the population. The description of congenital esotropia includes a constant esotropia confirmed at or before 6 months of age. The purpose of this study is to describe the early natural history of congenital esotropia from both an oculomotor and sensory standpoint. The ocular motility of approximately 2,800 infants per year will be examined in the newborn period between 3 hours and 3 days. These infants will then be followed from 3 days to 6 months of age in order to characterize the precursor stages and evolution of congenital esotropia. The following two hypotheses will be challenged: 1) Congenital esotropia is not present at birth, and 2) During the first 6 months of life, patients with congenital esotropia deviate from the normal course of sensory and oculo-motor development in a characteristic manner. The oculomotor status of infants during the first six months will be evaluated and recorded and, in addition, stereopsis will be tested using a dynamic random-dot stereogram technique. Standard treatment consisting of anti-accommodative measures, patching for amblyopia, and surgery will be carried out according to established principles. Postoperative evaluation of these treated children will be continued to determine the relationship of the chronology of strabismus onset, and time and accuracy of surgical realignments to motor and sensory results. Successful completion of this project promises the chance of improved understanding of congenital esotropia, leading to improved treatment techniques and results. Speculations about avenues for improved treatment techniques will arise with the accumulation of new information about how congenital esotropia develops.